The present invention relates to a liquid/product filling apparatus which utilizes a combination of pistons, cylinders and valves with a seal system for effectively preventing leakage of liquid or flowable products being handled by the apparatus.
Apparatus and process for automatically filling containers, such as cans and bottles, with both food and non-food products have become very sophisticated and efficient. Such apparatus and processes are used to fill containers with liquid, semi-liquid, pasty or products which might contain food products, such as liver paste, baby foods, jellies, vegetable oil, mustard, sauces, etc. and non-foods, such as mineral oil, wax, paints, etc. The apparatus used and the processes employed may take a variety of forms, one of the most popular being the so-called rotary piston filler, examples of which are disclosed in U.S. Pat. Nos. 4,501,622 and 4,602,964.
Rotary fillers typically include a generally cylindrical hopper made, for example, of stainless steel, a number of filling assemblies spaced apart about the exterior of the hopper, and a container or can conveying system for moving cans into position underneath the filling assemblies to receive product. The filling assemblies each typically include a vertically disposed cylinder, a valve coupling the lower end of the cylinder to the hopper and operable to either allow material to flow from the hopper into the cylinder or to flow from the cylinder into a can positioned below the valve, and a piston moveable in the cylinder to force material from the cylinder into the can. Rotary fillers also typically include a piston support structure for causing the pistons to move upwardly in the cylinders when product is flowing from the hopper into the cylinders, and downwardly when product is being forced from the cylinder into cans. See the aforecited U.S. Pat. Nos. 4,501,622 and 4,602,964.
An important aspect of rotary fillers such as described above is the seal system utilized to prevent leakage and flow of product to other than desired destinations to thus prevent contamination, maintain cleanliness, and reduce the loss and waste of product. One seal structure which has oftentimes been used in rotary fillers (and in many other applications) is the conventional O-ring. However, when used with the pistons, cylinders and valves employed in rotary fillers, it has been found difficult to keep the product from leaking or escaping behind the O-rings, especially if the product is liquid or flowable. Multiple O-rings are generally required to alleviate the problem of leakage in both piston and rotary valves and to provide proper sealing of pistons to develop adequate suction when the piston is used to draw food from the hopper to the cylinder prior to discharge of the food into a can.
The prior pistons and valves utilizing O-ring seals also present a problem during cleaning. Automatic cleaning systems have been suggested, as described in U.S. Pat. No. 4,502,622, for cleaning rotary fillers but if conventional O-ring seals were used in such fillers, it would be difficult to properly clean such seals. In fact, health concerns would generally require that these conventional O-ring seals be cleaned by hand since the O-rings would have to be removed from retainer grooves to clean both the O-rings and the grooves. This, of course, would negate some of the advantages of the automatic cleaning system.
One approach to overcoming, or at least alleviating, some of the problems of existing seal systems, as set forth in U.S. Pat. No. 4,844,481, which discloses a cylindrical seal system which utilizes O-rings in a manner which effectively prevents leakage and also allows for automated cleaning of the system. The present invention is a further improvement of this cylindrical seal system and seal systems especially adapted for use with rotary fillers.